An air separator on a gas turbine separates cooling air into two paths; one path leads into the row one turbine disc for cooling of the row one blade platform and the other path leads to the rotor for cooling of the rotor discs. A row one turbine disc is also known as a first row disc. The axial interference between the air separator and the row one turbine disc has been identified as a potential contributor to vibrations of the rotor. Loose axial interference can cause misalignment of rotor parts allowing them to move during operation or between starts causing excessive vibration. Excessive vibration, vibration above an acceptable threshold. can cause damage to the gas turbine with the damage sometimes severe enough to cause the gas turbine to be shut down. In the event of a gas turbine shutdown due to vibration excursions, the life of the turbine components may be reduced. General long term operation at high vibration levels may cause damage to the turbine and the components including the rotor, requiring early replacement or repair.